Source-Corrected Two-Photon Excited Fluorescence Measurements between 700 and 880 nm

1998 ◽  
Vol 52 (4) ◽  
pp. 536-545 ◽  
Author(s):  
W. G. Fisher ◽  
E. A. Wachter ◽  
Fred E. Lytle ◽  
Michael Armas ◽  
Colin Seaton
Keyword(s):  
Continuous Wave ◽  
Group Velocity Dispersion ◽  
Dispersion Compensation ◽  
Average Power ◽  
Single Mode ◽  
Wavelength Dependence ◽  
Power Correction ◽  
Two Photon ◽  
Fluorescence Measurements ◽  
Photon Excitation

Passively mode-locked titanium:sapphire (Ti:S) lasers are capable of generating a high-frequency train of transform-limited subpico-second pulses, producing peak powers near 105 W at moderate average powers. The low energy per pulse (<20 nJ) permits low fluence levels to be maintained in tightly focused beams, reducing the possibility of saturating fluorescence transitions. These properties, combined with a wavelength tunability from approximately 700 nm to 1 μm, provide excellent opportunities for studying simultaneous two-photon excitation (TPE). However, pulse formation is very sensitive to a variety of intracavity parameters, including group velocity dispersion compensation, which leads to wavelength-dependent pulse profiles as the wavelength is scanned. This wavelength dependence can seriously distort band shapes and apparent peak heights during collection of two-photon spectral data. Since two-photon excited fluorescence is proportional to the product of the peak and average powers, it is not possible to obtain source-independent spectra by using average power correction schemes alone. Continuous-wave, single-mode lasers can be used to generate source-independent two-photon data, but these sources are four to five orders of magnitude less efficient than the mode-locked Ti:S laser and are not practical for general two-photon measurements. Hence, a continuous-wave, single-mode Ti:S laser has been used to collect a source-independent excitation spectrum for the laser dye Coumarin 480. This spectrum may be used to correct data collected with multimode sources; this possibility is demonstrated by using a simple ratiometric method to collect accurate TPE spectra with the mode-locked Ti:S laser. An approximate value of the two-photon cross section for Coumarin 480 is also given.

Video-Rate Scanning Two-Photon Excitation Fluorescence Microscopy

1998 ◽  
Vol 4 (S2) ◽  
pp. 424-425
Author(s):  
G.Y. Fan ◽  
H. Fujisaki ◽  
R.-K. Tsay ◽  
R.Y. Tsien ◽  
Mark H. Ellisman
Keyword(s):  
Laser Beam ◽  
Group Velocity Dispersion ◽  
Laser System ◽  
Average Power ◽  
Laser Pulses ◽  
Green Laser ◽  
Two Photon ◽  
Photon Excitation ◽  
Schematic Layout ◽  
Two Photon Excitation

A video-rate scanning two-photon excitation microscope (TPEM) has been successfully constructed and tested. The TPEM, based on a Nikon RCM-8000, incorporates a femtosecond pulsed laser, a pre-chirper, and a non-confocal detection box for ratio imaging. Fig. 1 shows the schematic layout of the main components of the instrument, each of which is briefly discussed below.Laser System: A Tsunami Ti: Sapphire laser (from Spectra-Physics) is optically pumped by a 5 W green laser (Millennia from Spectra-Physics) and is capable of generating 100 fs pulses at a repetition rate of 82 MHz and an average power of 0.8 W. The output wavelength is tunable from 690 to 1050 nm with three optical sets, each covering part of the spectrum with some overlapping.Pre-chirper: After leaving the Tsunami, the laser beam enters an optic unit known as a pre-chirper which pre-chirps laser pulses to compensate for the group velocity dispersion which will result when the laser beam goes through the microscope optics.

Two-Photon near Infrared Excitation in Living Cells

1997 ◽  
Vol 5 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Karsten König
Keyword(s):  
Near Infrared ◽  
Continuous Wave ◽  
Cell Damage ◽  
Local Heating ◽  
Average Power ◽  
Two Photon ◽  
Photon Excitation ◽  
Non Linear ◽  
Linear Effects ◽  
Two Photon Excitation

Non-linear effects due to two-photon near infrared (NIR) excitation of endogenous and exogenous cellular chromophores allow novel techniques in tissue, cell and biomolecule diagnostics, as well as in intracellular micromanipulation (e.g. intracellular photochemistry). Two-photon NIR excitation may also result in cell damage effects. The high photon intensities (1024 photons cm−2 s−1) required for non-resonant two-photon excitation can be achieved by diffraction-limited focusing of continuous wave (cw) laser beams (cw microbeams) with powers in the mW range. For example, NIR traps (“laser tweezers”) used as force transducers and micromanipulation tools in cellular and molecular biology are sources of two-photon excitation. NIR traps can induce two-photon excited visible fluorescence and, in the case of <800 nm-traps, UVA-like cell damage. Multimode cw microbeams may enhance non-linear effects due to longitudinal mode-beating. To perform high scan rate two-photon fluorescence imaging, the application of ultrashort laser pulses of moderate peak power but low average power (pulsed microbeams) is required. In NIR femtosecond microscopes, non-destructive imaging of two-photon excited fluorophores in various human and culture cells was demonstrated for <2 mW average powers, <200 mW peak powers and 400 GW cm−2 intensities (700–800 nm, ∼150 fs, ∼100 MHz). However, higher average power levels may result in failed cell reproduction and cell death due to intracellular optical breakdown. In addition, destructive transient local heating and μN force generation may occur.

scholarly journals Continuous-wave two-photon excitation of individual CdS nanocrystallites

2001 ◽  
Vol 79 (6) ◽  
pp. 830-832 ◽  
Author(s):  
A. M. van Oijen ◽  
R. Verberk ◽  
Y. Durand ◽  
J. Schmidt ◽  
J. N. J. van Lingen ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

scholarly journals Measurement of the positronium 13S1–23S1interval by continuous-wave two-photon excitation

1993 ◽  
Vol 48 (1) ◽  
pp. 192-219 ◽  
Author(s):  
M. S. Fee ◽  
S. Chu ◽  
A. P. Mills ◽  
R. J. Chichester ◽  
D. M. Zuckerman ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

scholarly journals Passively Q-Switched and Mode-Locked Er3+-Doped Ring Fiber Laser with Pulse Width of Hundreds of Picoseconds

Photonics ◽  
2021 ◽  
Vol 8 (12) ◽  
pp. 560
Author(s):  
Ji Wang ◽  
Wenwu Zhang ◽  
Tianrun Zhang
Keyword(s):  
Fiber Laser ◽  
Continuous Wave ◽  
Average Power ◽  
Basic Research ◽  
Single Mode ◽  
Frequency Stability ◽  
Wave Mode ◽  
Switching Frequency ◽  
Maximum Output ◽  
Power Instability

Greatly improving the energy of a single mode-locked pulse while ensuring the acquisition of the width of short pulses will contribute to the application of mode-locked pulse in basic research, such as precision machining. This report has investigated a Q-switched and mode-locked (QML) erbium doped ring fiber laser based on the nonlinear polarization rotation (NPR) technology and a mechanical Q-switched device. Without the working of the mechanical Q-switched device, the fiber laser exported the continuous-wave mode-locked (CWML) pulse, with a width of 212.5 ps, and a repetition frequency of 81.97 MHz. For the CWML operation, the maximum output average power is 25.7 mW, and the energy is only 0.31 nJ. For the QML operation, 18.03 mW average power is achieved at the Q-switching frequency of 100 Hz. The energy of the QML pulse is increased by over 1100 times to 360.6 nJ. The width of the QML pulse is 203.1 ps measured by an autocorrelation curve, with the time-band product (TBP) being 0.598. The power instability is 0.5% (RMS) and 0.7% (RMS), respectively, for CWML and QML operation within 120 min. Furthermore, the spectral signal-to-noise ratio is about 60 dB. For the QML operation, the power instability is 0.48% (RMS) within 60 s and 0.37% (RMS) within 10 s. After frequency stabilization, the frequency fluctuation is ±100 Hz in the long-term of 1200 s, with the frequency stability (FS) calculated to be 2.44 × 10−6. It indicates that the QML fiber laser has good power stability and frequency stability.

scholarly journals Исследование мощности люминесценции экситонов и примесно-дефектных центров, возбуждаемых с помощью двухфотонного поглощения

2020 ◽  
Vol 54 (1) ◽  
pp. 48
Author(s):  
А.А. Гладилин ◽  
В.П. Данилов ◽  
Н.Н. Ильичев ◽  
В.П. Калинушкин ◽  
М.И. Студеникин ◽  
...  
Keyword(s):  
Radiation Power ◽  
Average Power ◽  
Electronic System ◽  
Quadratic Character ◽  
Degree Of Contamination ◽  
Two Photon ◽  
Defect Centers ◽  
Photon Excitation ◽  
Impurity Defect ◽  
Two Photon Excitation

In the present work, using as an example ZnSe: Fe2+ single crystals, it was experimentally and theoretically studied the effect of the average power of femtosecond laser radiation on the average luminescence power of excitons and impurity-defect centers upon two-photon excitation of the electronic system of a crystal. It has been experimentally shown that the average luminescence power of crystal excitons in the studied range of excitation powers is proportional to 4 degrees of the average excitation radiation power. The average luminescence power of impurity-defect centers has a quadratic character. A theory is constructed that explains the experimentally observed dependencies. It is noted that the nature of the dependence of the crystal luminescence on the pump power during two-photon excitation can be used to estimate the degree of contamination of the crystal by impurity-defect centers.

scholarly journals Measurement of the positronium13S1-23S1interval by continuous-wave two-photon excitation

1993 ◽  
Vol 70 (10) ◽  
pp. 1397-1400 ◽  
Author(s):  
M. S. Fee ◽  
A. P. Mills ◽  
S. Chu ◽  
E. D. Shaw ◽  
K. Danzmann ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation
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